I am heartened that you want to be able to help, so few do. Thank you.
The type and amount of help kind of depends on your friend. I think you have taken the first step in talking with her and being non-judgmental.
Allowing her to open up to you and talk frankly about her issues and needs can really be helpful. It can help her to sort out her feelings and the steps she wishes to take. This may not be something she has with her current relationship.
Also examine your own feelings. Will you still feel the same about her if she were to transition? Would you be willing to stand by her? Can you continue to be her friend? Or have a romantic relationship with a woman?
This is a very lonely path that we travel and to have a friend can make all the difference.
If you have any questions about what she may be facing, feel free to ask. Also, if she has not already, have her seek guidance from a gender therapist. And also, if she can, have her come here. There are many here to let her know she is not alone.
Thank you again for wanting to help. It can really mean so very much!
-Sandy